1. Field of the Invention
The present invention relates to a small or micro gas turbine engine, and more specifically to a fuel and air delivery structure that also is used to cool and lubricate the bearings.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Small or micro gas turbine engines are used for powering small unmanned air vehicles such as drones and missiles. In the early stages of development, larger gas turbine engines where simply scaled down to the required small size that would fit within the very limited space in these UAVs, or unmanned air vehicles. However, gas turbine engines are not readily scaled down in an effective cost proportional basis and a thrust proportional basis. As the gas turbine engine is reduced in size, the smaller sized rotors must operate at higher rotational speeds in order to achieve adequate performance levels. To take a regular gas turbine engine used in a typical modern jet would require the turbine parts to be reduced in size while operating the rotor shaft at much higher rotational speeds. At these high rotational speeds, the original designed parts such as the rotor shaft and the bearings would not be able to withstand the higher speeds. Rotor dynamics would cause the original design rotor shaft to vibrate so much that the shaft would explode. Also, the bearings would operate at speeds above the design speed. The bearings would burn up or vibrate so much that they would explode as well. Thus, it is an entirely new design challenge to take a regular gas turbine engine and scale it down to the size that would operate effectively in a small gas turbine engine powered vehicle.
The prior art gas turbine engine of Brooks et al, U.S. Pat. No. 5,526,640 issued on Jun. 18, 1996 discloses a small gas turbine engine with a rotor supported by bearings, and in which air and fuel is mixed and then passed through the bearings in order to cool the bearings prior to being burned in the combustor. A fuel slinger propels the air/fuel mixture into the combustor. A separate pump is used to enhance the slinger delivery of the fuel.
U.S. Pat. No. 6,925,812 B2 issued to Condevaux et al on Aug. 9, 2005 entitled ROTARY INJECTOR discloses a turbine engine with a rotary injector supported by ball bearings, and which in the FIG. 14b embodiment (of this patent) discloses that the forward and rearward roller bearings are respectively cooled by spraying pressurized liquid fuel in the first and second cylindrical grooves from respective orifices in a sleeve surrounding the central shaft between the pair of roller bearings (see column 7, lines 9-25).
U.S. Pat. No. 3,932,988 issued to Beaufrere on Jan. 20, 1976 entitled FUEL SLINGER COMBUSTOR discloses a fuel slinger combustor used in a gas turbine engine in which helical grooves are oriented on a rotary shaft to move fuel from grooves inwardly to grooves as the shaft rotates during operation of the engine and the fuel so moved is supplied via grooves to the radial bores of the slinger injector.
There is a need in the prior art for a small gas turbine engine with improved fuel efficiency in order to increase the hover time of the UAV. There is also a need in the prior art to decrease the overall size of the engine in order that the engine can be fitted in a small space. There is also a need in the prior art to reduce the cost of the small gas turbine engine without reducing the performance.
It is an object of the present invention to provide for a small gas turbine engine with bearings capable of being cooled such that a small engine is capable of operating at the required high speeds.
It is another object of the present invention to provide for a small gas turbine engine with lubricated bearings that is more efficient than the prior art engines.